Tension leg platform (tlp) having offset top tension riser (ttr) guides

ABSTRACT

A method of forming a tension leg platform (TLP) includes arranging a top tension riser (TTR) support system at one or more top tension risers, positioning the one or more top tension risers in corresponding ones of one or more TTR guide members supported by the TTR support system, connecting the TTR support system to a first column and a to a second column, and arranging a platform between the first and second columns.

PRIORITY CLAIM

This application is a non-provisional application which claims benefit under 35 USC §119(e) to U.S. Provisional Application Ser. No. 61/941,867 filed Feb. 19, 2014, entitled “TENSION LEG PLATFORM (TLP) HAVING OFFSET TOP TENSION RISER (TTR) GUIDES,” which is incorporated herein in its entirety.

FIELD OF THE INVENTION

This invention relates to systems for supporting top tension risers (TTR) and, more particularly, to a tension leg platform having offset TTR riser guides.

BACKGROUND OF THE INVENTION

A tension-leg platform (TLP) is a vertically moored floating structure typically used for the offshore drilling and capture of natural resources such as oil and/or gas. The TLP is formed by joining multiple columns with multiple pontoons to form a floating structure. The TLP is typically permanently moored to the sea floor by means of tethers or tendons that form a tension leg. The tension legs substantially eliminate all vertical motion of the TLP. In general, the TLP is anchored above or near a drilling location and supports one or more production wellheads that are connected directly to subsea wells by rigid risers. Typically, the rigid risers extend through a center portion of the TLP and connect with the production well heads. Often times it is necessary to load and unload equipment and supplies to/from the TLP. During such times, cranes move the equipment/supplies over the well heads and other structure on the TLP.

SUMMARY OF THE INVENTION

In accordance with and exemplary embodiment, a method of forming a tension leg platform (TLP) includes arranging a top tension riser (TTR) support system at one or more top tension risers, positioning the one or more top tension risers in corresponding ones of one or more TTR guide members supported by the TTR support system, connecting the TTR support system to a first column and a second column, and arranging a platform between the first and second columns.

In accordance with another exemplary embodiment, a tension leg platform (TLP) includes a first column, a second column spaced from the first column, and a top tension riser (TTR) support system extending between the first column and the second column. The TTR support system includes at least one TTR guide member configured and disposed to receive a TTR.

In accordance with yet another exemplary embodiment, a tension leg platform (TLP) includes a first column arranged on a first side of at least one top tension riser (TTR), a second column spaced from the first column on a second side of the at least one TTR. The first column, second column, and at least one TTR are in substantial alignment. A top tension riser (TTR) support system extends between the first column and the second column. The TTR support system includes at least one TTR guide member disposed about the at least one TTR.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with further advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying figures by way of example and not by way of limitation, in which:

FIG. 1 a side view of a tension leg platform (TLP) including a top tension riser (TTR) support system in accordance with an exemplary embodiment;

FIG. 2 is a top view of the TLP of FIG. 1; and

FIG. 3 is a top view of a TLP in accordance with another aspect of an exemplary embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the invention, not as a limitation of the invention. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention cover such modifications and variations that come within the scope of the appended claims and their equivalents.

A tension leg platform (TLP) constructed in accordance with an exemplary embodiment is illustrated generally at 2 in FIG. 1. TLP 2 includes a first column 4 extending from a first end portion 6 to a second end portion 7 through an intermediate portion 9. TLP 2 also includes a second column 12 spaced from first column 4. Second column 12 extends from a first end portion 14 to a second end portion 15 through an intermediate portion 17. First column 4 is arranged on a first side of a plurality of top tension risers (TTR) 28 and second column 12 is arranged on a second, opposing side of TTRs 28. In this arrangement, first column 4, second column 12 and TTRs 28 are in substantial alignment.

In accordance with an exemplary embodiment, TLP 2 includes a top tension riser (TTR) support system 40 connected to first and second columns 4 and 12. TTR support system 40 takes the form of a truss 44 that provides structural support to TLP 2. Truss 44 includes a plurality of TTR guide members 48 that receive respective ones of TTRs 28. In the exemplary embodiment shown in FIG. 2, TTR support system 40 includes a first plurality of TTR guide members (not separately labeled) extending along a first axis between first and second columns 4 and 12, and a second plurality of TTR guide members (also not separately labeled) extending along a second axis parallel to the first plurality of TTR guide members. Each of the first plurality of TTR guide members is substantially aligned with a corresponding one of the second plurality of TTR guide members. In addition, TLP 2 includes a deck or platform 54 that extends between, and is supported by, first and second columns 4 and 12 through corresponding platform support members 56 and 57, and provides a supporting surface (not separately labeled) for various pieces of equipment (not shown). As will become more fully evident below, TTR support system 40 enables TTRs 28 to be off-set from a center well (not separately labeled) of TLP 2 and secured in truss 44 to prevent clashing or undesirable contact. By off-setting TTRs 28 from the center well, equipment may be transferred to and from platform 54 without interfering or passing over existing structure/equipment.

In accordance with one aspect of an exemplary embodiment, TLP 2 includes four sides arranged in a generally rectangular geometry as shown in FIG. 2. In the exemplary aspect shown, TLP 2 includes a third column 63 and a fourth column 65. Third column 63 is arranged on one side of a plurality of TTR's 67 and fourth column 65 is arranged in a second, opposing side of TTR's 67. In a manner similar to that described above, third column 63, fourth column 65 and TTR's 67 are in substantial alignment. A first pontoon 72 extends from a first end 73 connected to first column 4 to a second end 74 connected to third column 63. A second pontoon 77 extends from a first end 78 coupled to second column 12 to a second end 79 coupled to fourth column 65. First and second pontoons 72 and 77 together with columns 4, 12, 63, and 65 provide support for platform 54. Another TTR support system 84 extends between third column 63 and fourth column 65. Another TTR support system 84 includes a truss 88 that provides additional structural support to TLP 2. Truss 88 also supports a plurality of TTR guide members 90 that receive TTR's 67. TTR guide members 90 are arranged in a manner similar to that described above in connection with TTR guide members 48. In a manner similar to that described above, another TTR support system 84 enables TTRs 67 to be off-set from a center well (not separately labeled) of TLP 2 and secured in truss 88 to prevent clashing or undesirable contact. By off-setting TTRs 67 from the center well, equipment may be transferred to and from platform 54 without interfering or passing over existing structure/equipment.

Reference will now be made to FIG. 3 in describing a TLP 100 in accordance with another aspect of the exemplary embodiment. TLP 100 includes a first column 104, a second column 106, and a third column 108 arranged in a generally triangular geometry. A TTR support system 111 extends between first column 104 and second column 106. In a manner similar to that described above, TTR support system 111 includes a truss 114 that provides structural support for TLP 100. TTR support system 111 also includes a plurality of TTR guide members 116 that receive, support, and maintain spacing between a plurality of TTR's 118. TLP 100 is also shown to include a first pontoon 124 that extends from a first end 125 coupled to first column 104 to a second end 126 coupled to third column 108. A second pontoon 130 extends from a first end 131 coupled to second column 106 to a second end 132 coupled to third column 108. A deck or platform 140 is supported by first, second, and third columns 104, 106, and 108.

At this point it should be understood that the exemplary embodiments provide a system for off-setting top tension risers (TTRs) from a center well of a tension leg platform while at the same time preventing undesirable clashing or contact. The present invention provides various benefits over existing systems. As will be detailed below, the benefits include a reduction in both construction and operational costs of an off-shore platform. In existing off shore platforms, TTRs may only be accommodated in the center well or outside of pontoons that support the platform. In contrast, the exemplary embodiment may accommodate the TTRs within the pontoons themselves. TTRs arranged in the center well may lead to interference with existing platform structures during loading and unloading of equipment and construction of the platform. TTRs arranged outside of the pontoons lead to an increase in structural steel weight necessary for the construction of the platform. As a consequence, hull size and tendon size must increase accordingly. Accommodating the TTRs within the footprint of the pontoons enables the loading and unloading of equipment to and from the platform without interfering with existing structure/equipment. In addition, accommodating the offset TTRs within the footprint of the pontoons leads to a reduction in the structural steel weight of the platforms thereby contributing to a reduction in overall hull and tendon size. Consequently, the introduction of the exemplary embodiments to an offshore platform leads to a significant cost savings in the size and weight of material as well as a reduction in overall operational costs of the offshore platform. Specifically, installation and operational costs of drilling equipment, particularly associated with tender assisted drilling (TAD) would be reduced.

The exemplary forms of the invention described above are to be used as illustration only, and should not be used in a limiting sense to interpret the scope of the present invention. Modifications to the exemplary embodiments, set forth above, could be readily made by those skilled in the art without departing from the spirit of the present invention.

While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims. 

What is claimed is:
 1. A method of forming a tension leg platform (TLP) comprising: arranging a top tension riser (TTR) support system at one or more top tension risers; positioning the one or more top tension risers in corresponding ones of one or more TTR guide members supported by the TTR support system; connecting the TTR support system to a first column and to a second column; and arranging a platform between the first and second columns.
 2. The method of claim 1, further comprising: connecting a first pontoon between the first column and a third column; and connecting a second pontoon between the second column and the third column, the platform extending across the first, second and third columns.
 3. The method of claim 1, further comprising: connecting a first pontoon between the first column and a third column; connecting a second pontoon between the second column and a fourth column; and connecting another TTR support system between the third column and the fourth column.
 4. The method of claim 3, wherein the platform is supported by each of the first, second, third, and fourth columns.
 5. A tension leg platform (TLP) comprising: a first column; a second column spaced from the first column; and a top tension riser (TTR) support system extending between the first column and the second column, the TTR support system including at least one TTR guide member configured and disposed to receive a TTR.
 6. The TLP according to claim 5, further comprising: a third column spaced from the first column and the second column; a first pontoon extending from a first end connected to the first column to a second end connected to the third column; and a second pontoon extending from a first end connected to the second column to a second end connected to the third column.
 7. The TLP according to claim 5, further comprising: a third column spaced from the first column and the second column; a fourth column spaced from the first column, the second column and the third column; a first pontoon extending from a first end connected to the first column to a second end connected to the third column; and a second pontoon extending from a first end connected to the second column to a second end connected to the fourth column.
 8. The TLP according to claim 7, further comprising: another TTR support system extending between the third column and the fourth column, the another TTR support system including at least one TTR guide member.
 9. The TLP according to claim 5, wherein the at least one TTR guide member extends substantially parallel to each of the first and second columns.
 10. The TLP according to claim 5, wherein the at least one TTR guide member includes a plurality of TTR guide members extending between the first and second columns.
 11. The TLP according to claim 10, wherein the plurality of TTR guide members includes a first plurality of TTR guide members extending along a first axis between the first and second columns and a second plurality of TTR guide members extending along a second axis substantially parallel to the first axis.
 12. The TLP according to claim 11, wherein each of the first plurality of TTR guide members is substantially aligned with corresponding ones of each of the second plurality of TTR guide members.
 13. A tension leg platform (TLP) comprising: a first column arranged on a first side of at least one top tension riser (TTR); a second column spaced from the first column on a second side of the at least one TTR, the first column, second column and at least one TTR being in substantial alignment; and a top tension riser (TTR) support system extending between the first column and the second column, the TTR support system including at least one TTR guide member disposed about the at least one TTR.
 14. The TLP according to claim 13, further comprising: a third column spaced from the first column and the second column; a first pontoon extending from a first end connected to the first column to a second end connected to the third column; and a second pontoon extending from a first end connected to the second column to a second end connected to the third column.
 15. The TLP according to claim 13, further comprising: a third column spaced from the first column and the second column, the third column being arranged on a first side of another TTR; a fourth column spaced from the first column, the second column and the third column, the fourth column being arranged on a second side of the another TTR, the third column, fourth column and another TTR being in substantial alignment; a first pontoon extending from a first end connected to the first column to a second end connected to the third column; and a second pontoon extending from a first end connected to the second column to a second end connected to the fourth column.
 16. The TLP according to claim 15, further comprising: another TTR support system extending between the third column and the fourth column, the another TTR support system including at least one TTR guide member disposed about the another TTR.
 17. The TLP according to claim 13, wherein the at least one TTR guide member extends substantially parallel to each of the first and second columns.
 18. The TLP according to claim 13, wherein the at least one TTR guide member includes a plurality of TTR guide members extending between the first and second columns.
 19. The TLP according to claim 18, wherein the plurality of TTR guide members includes a first plurality of TTR guide members extending along a first axis between the first and second columns and a second plurality of TTR guide members extending along a second axis substantially parallel to the first axis.
 20. The TLP according to claim 19, wherein each of the first plurality of TTR guide members is substantially aligned with corresponding ones of each of the second plurality of TTR guide members. 